1. Field of the Invention
This invention is directed to a molded plastic tank, for example a motor vehicle fuel tank, and, more specifically, to a molded plastic tank comprising an externally flanged, closed-section conduit at least partially embedded in a wall of the tank.
2. Brief Description of the Prior Art
Holding containers and tanks such as water tanks, motor vehicle fuel tanks and the like, referred to simply as "tanks" herein, often have attached to them in some fashion one or more tubes, hoses or other such conduits. Fuel return lines, fuel vapor venting lines, and the like associated with the motor vehicle fuel tank, for example, typically are attached in some fashion to the tank at one or more points. It is known for this purpose to use a hot plate welding technique in which a plastic conduit and the surface of a plastic tank wall are partially melted while being pressed into contact with each other so as to be fused together. It is difficult to control such hot plate welding techniques, however, in view of the natural variation in material properties, dimensions, and ambient conditions. Accordingly, there is a need to provide a better process and design for attachment of conduit to a molded plastic tank. It is an object of the present invention to provide such product design and method of manufacture.
In U.S. Pat. No. 3,666,139 issued May 30, 1972 to Urban, a container is disclosed, described as being especially suitable as a fuel tank for motor vehicles, in which a top wall and an opposite side wall of the tank comprise a plurality of conduits for connecting the interior of the container with the atmosphere. That is, the tank is shown to have a plurality of vent lines. Each such vent line has a substantially horizontal section extending from an opening in the interior at one side wall toward the opposite side wall. Each such horizontally extending section bends sharply upward toward a remote vent opening. No detail is given regarding the manner in which the vent lines are attached to the fuel tank.
In U.S. Pat. No. 3,687,335 issued Aug. 29, 1972 to Hunter, a motor vehicle fuel tank is shown to comprise overfill limiting means. Specifically, a fuel tank is shown to have vent means, such as a plurality of vent lines which are positioned one each in the upper fuel tank corners. The vent lines pass through a wall in the tank and extend within its interior to the remote corners of the tank. No teaching is provided regarding particular means for attachment of the vent lines to the fuel tank.
In U.S. Pat. No. 3,575,949 issued Apr. 20, 1971 to Humphrey, a method is disclosed by which a tubular passageway can be incorporated into the wall of a blow-molded container. In the Humphrey method an elongated, open-section element is positioned within a blow molding tool and the container is blow molded against such element such that the plastic wall of the blow-molded container fuses with and closes the open-section channel-defining element to form therewith a tube. As best seen in FIGS. 5 and 6 of Humphrey, the open-section element does not itself define a channel able to contain a fluid flow but, rather, depends upon forming a perfectly complete perimeter seal with the tank wall blow molded against it. Because of this disadvantageous requirement and to prevent the conduit element of Humphrey pulling away from the container wall, the method of Humphrey requires that the material of the conduit element be fusible with the material from which the container is to be blow-molded. Thus, Humphrey suggests it to be desirable that the conduit element and the container wall be of the same material.
It is an object of the present invention to overcome the disadvantages of the prior art. In particular, it is an object of the invention to provide a process and a product wherein a conduit is provided in a tank wall, the conduit and tank wall optionally being of materials non-fusible with each other. It is further an object of the invention to provide such process and product wherein a perfectly continuous fusing or seal between the container wall and the conduit is not required either to ensure a fluid-tight conduit or to ensure against the conduit pulling out of or away from the tank wall.